In the current technology, methods for manufacturing circuits of circuit boards can be divided into two types: dry film etching process and semi-additive process. The dry film etching process is a method using ways of tents as shielding for manufacturing the circuit line. The circuit board uses dry films as protecting covers on through holes of the circuit board, to prevent etching solution from entering into the through holes and etching away copper on inner wall of the through hole. In recent years, a method directly using photoresist to protect copper face to do direct etching, without circuit electroplating, is generally called as tenting. The semi-additive process is an additive process including chemical deposition of metal on a face of an insulating base, electroplating and/or etching to from conductive pattern. A process of the semi-additive process includes: drilingl hole, catalytic treatment and viscous treatment, chemical copper plating, imaging (electroplating resist), graphical electroplating copper (negative phase), remove of the resist, and differential etching.
The dry film etching process generally is a first choice for manufacturing the circuit lines, because of the short process and low cost thereof, but because of the trapezoidal cross-section and the thickness of the copper layer and uniformity, the circuit line less than 35/35 μm is difficult to be manufactured by this method. At present, it can match with two fluids to etch to manufacture the circuit line of 25/25 μm, but it has higher requirements to the thickness of the copper layer and the uniformity. In addition, because of adjustment of the uniformity (or variation of the thickness of the copper layer), the process for manufacturing a fine circuit line is prone to over etch to result in the circuit line too thin or broken (as shown by a circled part A in FIG. 1), while no etch is prone to result in micro-short (as shown by a circled part B in FIG. 1), it is very difficult to repair after manufacture, which causes low yield.